Two-stage carburetor



March 13, 1962 M. A. GEHNER TWO-STAGE CARBURETOR 2 Sheets-Sheet 1 Filed Feb. 6, 1956 vs II h CL INVENTOR. MAURICE A.GEHNER Z WM ATTORNEY March 13, 1962 M. A. GEHNER 3,025,039

TWO-STAGE CARBURETOR Filed Feb. 6, 1956 2 Sheetsmsheet 2 FIG.4.

FIG 5 PERCENTOF STROKE 0 I0 .30 so so a0 Q Q Q Q Q 2 co 0 q- M PERCENT CURRENT INVENTOR. MAURICE A. GEHNER ATTOPNEY States Patent @ffiee IifiZSfiEQ Patented Mar. 13, 1962 3,025,039 TWD-STAGE CARBURETOR Maurice A. Gehner, Pagedale, Mo., assignor, by mesne assignments, to ACE Industries, Incorporated, New York, N.Y., a corporation of New Jersey Filed Feb. 6, 1956, Ser. No. 563,529 Claims. (Cl. 261-23) This invention relates to multi-stage carburetors and, more particularly, to a novel mechanism for automatically operating the throttle or throttles in the secondary stage or stages of a multi-stage carburetor.

This invention is specifically applicable to operate the secondary throttles of a four-barrel carburetor such as shown in the patent to Bicknell 2,640,472, but it may be adapted to automatically operate the throttle or throttles in any multi-stage carburetor system.

In prior mechanisms for this purpose, such as shown in Ericson et al., 2,355,716, the secondary throttle is operated automatically by a suction motor deriving its power from the carburetor venturi or manifold. The secondary throttle valve or valves are balanced, and it is the usual practice to hold these automatic valves closed against the force applied by the suction motor by a constantly acting force such as a spring. Because there are only two forces acting in such mechanisms, the spring in one direction, and the motor in the opposite direction, it is difficult to calibrate the initial action, degree of response, and rate of response, unless the motor has a large piston and the spring is a low-rate spring. The limited space available rules out the use of a large suction motor. This, in turn, means that, with a suction motor and spring of acceptable size, the system leaves something to be desired in the way of sensitivity.

According to the present invention, a suction operated switch is connected with the primary venturi, and this switch is constructed to be operated by small changes in pressure, so that its action in the closing and opening directions is immediately responsive to small changes in pressure. The switch controls an electric circuit energized by primary throttle opening, and supplies power to a motor for automatically opening the secondary throttles. This system has the advantage of the required degree of sensitivity in initial action, and may be modified to give the required degree of response and the required rate of response independently.

This will appear more obvious after a reading of the accompanying detailed description of the invention taken with the drawings, in which:

FIG. 1 is a schematic representation of an embodiment of the carburetor and its control system.

FIG. 2 is a side elevation view, partly in section, of a four-barrel carburetor equipped with a switch and motor for operating the secondary throttle according to the present invention.

FIG. 3 is an operational view showing the action of the throttle mechanism.

FIG. 4 is a schematic representation of another embodiment of a system for automatic control of the throttles of a four-barrel carburetor.

FIG. 5 is a graph showing motor force plotted against spring resistance.

Referring to FIG. 1, battery B has one terminal connected with ground G, and the other connected with switch S through manually operated switch M. An electric motor E is connected with switch S and also with ground G. The carburetor'C which mounts the switch S and motor E has primary throttles 11 connected for manual operation to the accelerator pedal A through the links L and L and bellcrank D, which has a finger F for operating the switch M. The linkage L and L connects the accelerator pedal A directly with the primary throttle shaft of a carburetor C.

The carburetor and control system is shown more clearly in FIGS. 2 and 3, and it is contemplated that the sys tem described can be applied to any multi-stage carburetor, the construction of which may correspond, for example, with that described in detail in the aforesaid patent to Bicknell. Only so much of the structure of the carburetor C will be described as will enable one skilled in the art to understand the present invention.

According to conventional practice, the carburetor C has a primary throttle shaft it) which mounts a pair of primary throttle valves 11, one of which is shown. Fixed on the outer end of the throttle shaft 10 is a lever 12 which, in turn, carries an integrally forced cam 13 having a cam face 14 for cooperation with a similar cam face 23 on a lever 22 moving with the secondary throttles, later described. Lever 12 has an integral finger 1 .5 in abutting relation with a lug 16 on lever 1'7 freely rotatable on the primary throttle shaft 10.

The secondary throttle shaft 20 carries a pair of throttle valves 21, one of which is shown. Fixed to the outer end of the shaft 20 is the lever 22 having the integrally formed cam face 23 formed on the arm 24 for cooperation with the cam face 14. An oppositely directed arm on the lever 22 carries a pin 26 to which is attached a spring 27 tensioned between the eye 28 and the bracket 26. The spring is arranged to travel over center so as to urge the throttles closed when on one side of center and open when on the other. Extending between the levers 17 and 22 is a connecting link 29.

A port or nozzle 30 in the primary mixture conduit, controlled by the primary throttles, has a passage 31 extending through the body of the carburetor to a threaded connection 32 which receives the nipple 33 of a suction operated switch S. Suction at port 30 .is conveyed by passage 31 to one side of a diaphragm 34 by way of a passage 35 within the nipple 33. A plunger 36 is attached securely to the diaphragm 34 and operated thereby. A spring 37 surrounds the plunger .36 and is compressed between the head 38 and a bridge portion 39 within the casing 40 of the switch S. A fixed switch point 41 is carried by a bracket 42 connected with the terminal 43 of the switch. A block of insulating material 44 forms a fixed mounting for the fixed terminal 4-1, and also for the spring 45 carrying the movable contact 46. The spring 45 connects with the opposite terminal 48 of the switch 8.

Also mounted on the body of the carburetor C is an electric motor E, which has a pair of electric terminals 50 and 51 which connect with the field winding 52 of the motor E. Slidably mounted within the field is a core or armature 54 having a rod-like extension 55 carrying a hook 56. The hook 545 is positioned for engagement with one arm of the lever 22. When the motor E is energized, the core 5 moves into engagement with the guide plate 58, which limits the extreme movement of the core within the field, and hook 56 engages lever 22, opening throttles 21.

The motor E moves the secondary throttles 21 in the opening direction far enough so that the spring 27 passes beyond its dead-center position, as shown in FIG. 3. Cam surfaces 23 and 14 can limit the opening of the secondary throttles in a manner to be described hereinafter.

Operation Turning now to FIG. 1, as the accelerator pedal A is moved in a direction to open the primary throttles 11, finger F will engage and close switch M. Continued movement of the accelerator is permitted by the switch to move the primary throttles to the wide-open position,

as is customary. Throttle return spring T will close the primary throttles when pressure is removed from accelerator A. This linkage is preferably designed so the switch M closes after the primary throttles have been opened half-way, but the linkage can be made adjustable to vary the setting.

With switch M closed, the power of the battery B is communicated by way of terminal 4% to the switch S. As the velocity of flow through the primary mixture conduits past the port 30 increases with primary throttle opening and engine speed, static depression at this port will increase. For proper calibration of the spring 37, the switch S can be arranged to close when the degree of suction corresponds with a predetermined relation between engine speed and throttle opening. Usually the switch is so calibrated as to close in response to static pressures of less than one to one-and-a-half inches of mercury suction.

Closing of the switch S energizes the control circuit and the electric motor E and pulls the solenoid 54 to the left against the resistance of spring 27. When the spring 27 passes its dead-center position, however, the secondary throttles will open to a degree permitted by the cooperating cam surfaces 23 and 14, above described, under the influence of spring pressure. The lost motion connection between levers 12 and 17 through finger 15 and lug 16 will permit the primary throttles to open without interference with the operation of the secondary throttles. However, when the primary throttles are moved toward closed position, cams 23 and 14 engage so as to move the secondary throttles closed. Both sets of throttles will be moved closed simultaneously by spring T. In the closed position of the primary throttles, finger 15 engages lug 16 to hold the secondary throttles closed by lever 17 and link 29.

The carburetor C'may also have a mechanism for preventing operation of the secondary throttles so long as the automatic choke is in operation. It is contemplated that such a mechanism as shown in the patent to D. M. Gordon, 2,681,213 of June 15, 1954, may be used to latch the secondaries closed under such circumstances.

In the mechanism above described, the pressure drop in the primary mixture conduits is relied upon to operate only the switch S, which can be made as sensitive a control as desired. In this respect, this construction diiters from prior constructions in which the degree of suction in the primary mixture conduits actually furnishes the opening power applied by the suction motor connected to the secondary throttles.

FIG. 4 is a schematic representation of a modification of the system shown in FIGS. 1 to 3. Similar reference characters will be used to indicate like parts.

In this modification, a battery B has one terminal connected with ground G, and its other terminal connected with a switch M positioned to be operated by a finger F of a bellcrank D. The other terminal of the switch M connects with a brush P operating on a rheostat R, in turn connected with one terminal of electric motor E. The opposite terminal of the motor is connected with ground G. The brush P is, in turn, moved on the rheostat R by a suction motor W.

The primary and secondary mixture conduits of the carburetor C are indicated as 1 and 2, respectively. Primary throttle shaft 11 is operated from the accelerator pedal A through the links L and L and carries primary throttles 11.

The secondary throttles 2 1 are mounted on the secondary throttle shaft 20 having a fixed lever 22 thereon operated by a link 55 from the core or armature 54 of the electric motor E. The linkage is so arranged that the armature 54 is about 30 percent within the field 52 when the secondary throttles 21 are closed. Full opening of the throttles 21 is accomplished by movement of the armature 54 to a position about 80 percent within the field 52 and is resisted by a spring 27. An extension 54 on the end of the armature 54 engages with the cover plate 58 of the electric motor E to limit the travel of the armature to this amount.

Suction motor W has a casing 40 mounting a flexible diaphragm 34 positioned within the casing by a pair of bucking springs 37 and 37. A port 30 within the primary mixture conduit 1 communicates static pressure by way of passage 3-1 to one side of the diaphragm 34. The initial position of the parts in the absence of suction is shown in FIG. 4.

Operation This mechanism provides separate calibration for all three variables-that is, initial action, degree of response, and the rate of response of the secondary throttle to the degree of suction in, the primary mixture conduit 1 at the port 30.

For example, the motor W may be calibrated to have a linear response to the degree of suction at the port 30, or a non-linear response, whichever is desirable. If its response is linear, then each increasing degree of suction will cause a like movement of the brush P, and this, in turn, will produce a linear response from the electric motor E, as explained by an examination of the disclosure in FIG. 5, which is a graph plotting percentage of force X generated by the electric motor against the force of a spring Y. Each of the curves X indicates the force generated from 0 current to saturation 100 percent, and it can be seen that between 30 and percent of the stroke this force is a constant in each instance. Also plotted on FIG. 5 is the curve Y which represents the force of the spring 27 in opposition to the action of the electric motor E. Where the spring is compressed from 30 percent to percent of its total resistance, its reaction will be a straight line, approximately, shown by the curve Y. Obviously, a variable rate spring can be substituted if a non-linear reaction is desired. In the case illustrated, however, each increase in current will produce like displacements of the armature 54 within the electric motor, and the degree of these displacements will be indicated at the intersection of the curves X and Y, so that linear displacements may be had with linear increases in current in the motor B. These displacements, in turn, will occur due to the increase in current as the resistance of the rheostat is reduced by movement of the brush P by the motor W.

With this mechanism, as the primary throttles 11 are opened by accelerator A, the switch M is closed, energizing the electric circuit to brush P. As stated above, this event can occur at any degree of throttle opening by making linkage L and L adjustable. After the switch M closes, operation of the secondary throttles depends upon engine speed, which determines the degree of suction at port 3d. The action of increasing suction moves diaphragm 34 to the right against the resistance of spring 37. If a second spring 37' is used, it will aid the action of suction, and the response of motor W will be nonlinear. This spring may be omitted if a linear response is desired.

The response of motor W to increase in suction moves brush P over rheostat R, producing a linear increase in current to motor E, which will respond as described above. When pressure is released from accelerator A, spring T closes throttles 11, decreasing the suction at port 30 and finally de-energizing the circuit by opening switch M. Spring 27 can expand as suction decreases to close throttles 21, but a mechanical closer such as described in FIG. 3 may be used with this modification if desired.

A device has been described which will fulfill all the objects of the invention as stated above, but it is contemplated that other modifications will occur to those skilled in the art which come within the scope of the appended claims.

I claim:

I. In a multi-stage carburetor having primary and secondary mixture conduits, the combination of a manually operated primary throttle in said primary mixture conduit, a secondary throttle in said secondary mixture conduit, and mechanism for operating said secondary throttle comprising a means for sensing the degree of primary throttle opening and engine speed and fully responsive within a small range of changes of said variables, a source of power, means to vary the output of power from said source operated by said sensing means in a degree corresponding to the response of said sensing means, and a motor powered from said source connected to said secondary throttle and constructed to respond in a predetermined amount to changes in power input from said source.

2. A multi-stage carburetion system comprising primary and secondary mixture conduits having, respectively, primary and secondary throttle valves therein, yielding means normally closing said secondary throttle valve, an electro-magnetic motor and a source of power therefor for opening said secondary valve, and means responsive to predetermined suction conditions in said primary mixture conduit tube for connecting said motor and source of power to cause opening of said secondary throttle, and means in said connecting means for energizing said electro-magnetic motor and opening said secondary throttle proportionately with predetermined changes in rate of airflow in said primary conduit.

3. In a multi-stage carburetor having primary and secondary mixture conduits, the combination of a manually operated primary throttle in said primary mixture conduit, a secondary throttle in said secondary mixture conduit, and mechanism for operating said secondary throttle comprising a means for sensing the degree of primary throttle opening and engine speed and fully responsive within a small range of changes of said variables, said sensing means including a suction motor and a passage connecting said suction motor to said primary mixture conduit upstream of said primary throttle, a source of power, means to vary the output of power from said source operated by said sensing means in a degree corresponding to the response of said sensing means, and a motor powered from said source connected to said secondary throttle and constructed to respond in a predetermined amount to changes in power input from said source.

4. In a multi-stage carburetor having primary and secondary mixture conduits, the combination of a manually operated primary throttle in said primary mixture conduit, a secondary throttle in said secondary mixture conduit, and mechanism for operating said secondary throttle comprising a means for sensing the degree of primary throttle opening and engine speed and fully responsive within a small range of changes of said variables, said sensing means including a suction motor and a passage connecting said suction motor to said primary mixture conduit upstream of said primary throttle, a source of electrical power, a rheostat having a variable resistance connected to said power source to vary the output of power from said source, a control for said rheostat connected to said suction motor to be operated thereby in a degree corresponding to the response of said suction motor, and an electro-magnetic motor connected to said rheostat to be powered from said source and operatively connected to said secondary throttle and constructed to respond in a predetermined amount to changes in power input from said source.

5. A multi-stage carburetion system comprising primary and secondary mixture conduits having, respectively, primary and secondary throttle valves therein, yielding means normally closing said secondary throttle valve, an electro-magnetic motor and a source of electrical power therefor for opening said secondary valve, and means including a suction motor connected by a passage to said primary mixture conduit upstream of said primary throttle and responsive to a predetermined range of changes in air flow through said primary mixture conduit, said means also including an electrical circuit connecting said motor and source of power to cause opening of said secondary throttle, and a rheostat in said circuit between said source of power and said electro-magnetic motor and operatively connected to said suction motor for energizing said electro-magnetic motor and opening said secondary throttle proportionately with predetermined changes in rate of air flow in said primary conduit.

References Cited in the file of this patent UNITED STATES PATENTS 2,159,405 Schubert May 23, 1939 2,445,098 Wirth July 13, 1948 2,573,477 McIntosh Oct. 30, 1951 2,600,368 Winkler June 10, 1952 2,640,472 Bicknell June 2, 1953 FOREIGN PATENTS 734,667 Great Britain Aug. 3, 1955 1,069,312 France Feb. 10, 1954 

